XArray: Add xas_advance()

Add a new helper function to help iterate over multi-index entries.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index a91e3d90df8a..d6d5da6ed735 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -1581,6 +1581,24 @@ static inline void xas_set(struct xa_state *xas, unsigned long index)
 }
 
 /**
+ * xas_advance() - Skip over sibling entries.
+ * @xas: XArray operation state.
+ * @index: Index of last sibling entry.
+ *
+ * Move the operation state to refer to the last sibling entry.
+ * This is useful for loops that normally want to see sibling
+ * entries but sometimes want to skip them.  Use xas_set() if you
+ * want to move to an index which is not part of this entry.
+ */
+static inline void xas_advance(struct xa_state *xas, unsigned long index)
+{
+	unsigned char shift = xas_is_node(xas) ? xas->xa_node->shift : 0;
+
+	xas->xa_index = index;
+	xas->xa_offset = (index >> shift) & XA_CHUNK_MASK;
+}
+
+/**
  * xas_set_order() - Set up XArray operation state for a multislot entry.
  * @xas: XArray operation state.
  * @index: Target of the operation.